Fe-Mn-Al-C Alloy Steels - A New Armor Class
Program Executive Office Ground Combat Vehicles Warren United States
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Fe-Mn-Al-C alloy steels are being ballistically characterized by the Tank Automotive Research Development and Engineering Command TARDEC and the Army Research Lab ARL as a Class V Rolled Homogeneous Armor RHA Grade under MIL-A-12560. This paper summarizes the prior body of work regarding ballistic investigation leading up to the current Class V development. Physical and metallurgical characterization with limited ballistic tests has occurred by ARL1,2. Fe-Mn-Al-C alloys were investigated since they possess lower density 6.5 to 7.2 gcm3 versus standard steel chemistries 7.8 gcm33, tensile strengths from 600 to 2,000 MPa, and elongation to failure as great as 70. These alloys are near non-magnetic, and they can exhibit high-energy absorption within a chemistry range of Fe-10-30Mn-5-15Al. High strain rate testing has shown that as strength increased with strain rate, ductility exceeded 30 at 1000 s-1, indicating that ballistic evaluation would be favorable, even in a cast form3,4,5. A ballistic test and report was conducted on a Fe-13Mn-10Al-1C wrought alloy in 19792, an extensive investigation into a cast Fe-30Mn-9Al-1Si-0.9C-0.5Mo alloy was conducted between 2006 and 20101, and a wrought form of the Fe-30Mn-9Al-1Si-0.9C-0.5Mo alloy was ballistically tested in 2008 which has not been previously reported.